(USER_H): Files in ginclude now. Add stdarg.h,

(USER_H): Files in ginclude now.  Add stdarg.h,

stddef.h, varargs.h.
(all.cross, rest.encap): Move LIBGCC after stmp-headers.  Add
objc-runtime, and SYSCALLS.c.X.
(for-bootstrap): Delete.
(OBJC, OBJECTIVE-C): Delete objc-runtime.
(proto): Delete SYSCALLS.c.X.
(*.o): Delete gvarargs.h dependencies.
(stmp-int-hdrs): Delete gvarargs.h, gstdarg.h, gstddef.h deps, and
code to copy them.

From-SVN: r6955